`curve.tAtLength(length [, opt])`

Return the `t`

value of the point that lies `length`

away from the beginning of the curve.

If negative `length`

is provided, the algorithm starts looking from the end of the curve. If `length`

requested is higher than curve length, the `t`

of the closest curve endpoint (0 or 1) is returned instead.

The curve is first subdivided, according to `opt.precision`

(refer to `curve.length()`

documentation for more information about precision and curve flattening). Then, one subdivision is identified which contains the point at `length`

. A binary search is then performed on that subdivision, until a curve is found whose endpoint lies within `opt.precision`

away from `length`

. The `t`

value of that endpoint is returned by the function.

The default value for `opt.precision`

is 3; this corresponds to maximum observed error of 0.1%.

The `opt.subdivisions`

property may be specified, directly providing an array of pre-computed curve subdivisions from which to calculate curve length. Use the `curve.getSubdivisions()`

function to obtain an array of curve subdivisions. The `opt.precision`

property is still necessary, however; it determines the precision of the point search algorithm.